// let str = "欢迎使用TS"
// console.log(str)


// let str1: string = "北京欢迎你"
// let num1: Number = 100
// let tag: Boolean = true
// let a: null = null
// let b: undefined = undefined
// let c: Symbol = Symbol("北京")

// 联合类型
let address: (number | string) = 100
address = "北京"






